Wikipedia is free content, meaning that it may be freely used, freely edited, and is free to copy and redistribute. As such, Wikipedia is subject to some unique hardships that do not exist in traditional paper encyclopedias nor in copyrighted software encyclopedias. It has self-healing systems in place to deal with these challenges, and even a page designed to explain these systems.

The Chinese emperor Chengzu oversaw the compilation of the Yongle Encyclopedia, one of the largest encyclopedias in history, which was completed in 1408 and comprised over 11,000 handwritten volumes, of which only about 400 now survive.

The early Muslim compilations of knowledge in the middle ages included many comprehensive works, and much development of what we now call scientific method, historical method, and citation. Notable works include Abu Bakr al-Razi's encyclopedia of science, the MutaziliteAl-Kindi's prolific output of 270 books, and Ibn Sina's medical encyclopedia, which was a standard reference work for centuries. Also notable are works of universal history (or sociology) from Asharites, al-Tabri, al-Masudi, Ibn Rustah, al-Athir, and Ibn Khaldun, whose Muqadimmah contains cautions regarding trust in written records that remain wholly applicable today. These people had an incalculable influence on methods of research and editing, due in part to the Islamic practice of isnad which emphasized fidelity to written record, checking sources, and skeptical inquiry.

However, these works were rarely available to more than specialists: they were expensive, and written for those extending knowledge rather than (with some exceptions in medicine) using it. The modern idea of the general purpose widely distributed printed encyclopedia goes back to just a little before Denis Diderot and the 18th century encyclopedists. Major university libraries can be seen as museums of monumental encyclopedic endeavors in various countries. Frequently found titles are the EnglishEncyclopædia Britannica, the SpanishEnciclopedia Universal Illustrada, the GermanMeyers Konversations-Lexikon and Brockhaus. See encyclopedia for more information.

One pertinent issue on Wikipedia is "vandalism": silly or offensive edits to its encyclopedia articles. For example, Sarah Lane, presenter of "Sarah's Blog Report," part of The Screen Savers TV program on TechTV, "vandalised" the Wikipedia page on monkeypox live on air [1] - leading to a surge of vandalism on that page by viewers of the TV show. Lane later wrote that "Although this excites me in its ease and simplicity, it's a little frightening. I mean, what if I had instead written 'My boss is a big fat **** and his phone number is ****'? Sure, somebody would delete it, but this calls for some seriously dedicated moderators." [1]

"Because Wikipedia is a radically free, open project, it attracts an anarchistic element," Larry Sanger, co-founder of Wikipedia, admitted to Wired News. "Fortunately, most of us are willing to take a definite stand against vandalism ... and to get rid of it instantly."

According to a Wall Street Journal article from February 2004, researchers have found that instances of vandalism at Wikipedia are often quickly resolved: Recent research by a team from IBM found that most vandalism suffered by Wikipedia had been repaired within five minutes. That's fast: "We were surprised at how often we found vandalism, and then surprised again at how fast it was fixed," says Martin Wattenberg, a researcher in the IBM TJ Watson Research Centre, in Cambridge, Mass. ([1])

First, because there is a huge variety of participants of all ideologies, and from around the world, Wikipedia is committed to making its articles as unbiased as possible. The aim is not to write articles from a single objective point of view -- this is a common misunderstanding of the policy -- but rather, to fairly present all views on an issue, attributed to their adherents.

Second, there are a number of article naming conventions; for example, when several names exist, the most common one in the respective Wikipedia language is to be used.

Third, Wikipedians use "talk" pages to discuss changes to the text, rather than discussing the changes within the text itself. Concerns which seem to span many articles may require a more general treatment at Meta-Wikipedia or on the mailing lists.

Fourth, there are a number of kinds of entries which are generally discouraged, because they do not, strictly speaking, constitute encyclopedia articles. For example, Wikipedia entries are not dictionary definitions, and the wholesale addition of source material such as the text of laws and speeches is generally frowned upon.

Fifth, there are a variety of rules, guidelines, policies, and common practices that have been proposed and which have varying amounts of support within the Wikipedia community.

There is no editor-in-chief, as such. The two people who founded Wikipedia are Jimmy Wales (CEO of the small Internet companyBomis, Inc.) and Larry Sanger. For the first thirteen months, Sanger was paid by Bomis to work on Wikipedia. Sanger was said to have taken a role of mediator at times, making decisions on issues of heated debates. This was based not on formal authority, but on demands from users at large. Funding ran out for his position, leading to his resignation in February of 2002. Other current and past Bomis employees who have done some work on the encyclopedia include Tim Shell, one of the co-founders of Bomis, as well as programmers Jason Richey and Toan Vo.

The particular version of wiki software that originally ran Wikipedia was UseModWiki, written by Clifford Adams ("Phase I"). First it required CamelCase for links; soon it was also possible to use the current linking method with double brackets. In January 2002, Wikipedia began running on PHPwiki software, which used an underlying MySQLdatabase, added many features (and abolished the behaviour of CamelCase words automatically becoming links), and was specifically written for the Wikipedia project by Magnus Manske ("Phase II"). After a while, the site started to slow down to an extent where editing became almost impossible; several rounds of modifications to the software provided only temporary relief. Then Lee Daniel Crocker rewrote the software from scratch; the new version, a major improvement, has been running since July 2002; this "Phase III" software is now also called MediaWiki. Brion Vibber has since taken the lead in fixing bugs and tuning the database for performance.

In late 2003, server outages had become a serious problem to Wikipedia contributors. Many of them reported they had difficulty editing articles by getting time-outs and severe slowness. This was due to congestion on the single server that was running all the Wikipedias at the time.

The project now runs on nine dedicated servers, located in Florida. The new configuration currently includes a single database server and four web servers, which serve up pages as requested, performing page rendering for all the Wikipedias. To increase speed further, rendered pages for anonymous users are cached in a filesystem until rendered invalid, allowing page rendering to be skipped entirely for most common page accesses. Cached requests are served by two Squid servers; the new servers are linked via two file system NFS servers (one primary and one backup - the primary NFS server is currently also the email server).

Nupedia, a slow-moving project to produce a free peer reviewed encyclopedia. Nupedia shut down on September 26, 2003, and much of its content has since been assimilated by Wikipedia.

Everything2 has a wider range and does not exclusively focus on building an encyclopedia; its contents are not available under a copyleft license.

Indymedia, which focuses on networking first-hand source material from local, diverse groups of people around the world, linking grassroots, non-virtual social reality and the internet community.

H2G2, a collection of sometimes humorous encyclopedia articles, based on an idea from Douglas Adams's The Hitchhiker's Guide to the Galaxy. Articles are not freely redistributable.

EvoWiki is "a Wiki about evolution and origins. The focus is on evolution education, particularly addressing the arguments of Creationism and Intelligent Design from the perspective of mainstream science. It is inspired by webpages such as talkorigins.org and talkdesign.org, and the goal of EvoWiki is to complement rather than duplicate these online resources".

PlanetMath is a free Wiki-style mathematical encyclopedia which was originally built to replace MathWorld, a proprietary system hosted at Wolfram Research which was down for some time due to legal difficulties. Since MathWorld has returned, PlanetMath has still thrived.

Gnupedia, an initiative which didn't come to fruition but had some interesting philosophy.